However, the US retail giant has created its own agreement, which it claims goes beyond the current accord that was drafted by labour groups and campaigners.

The company, which also owns the UK's third biggest supermarket, Asda, said the deal signed by its rivals was "unnecessary to achieve fire and safety goals" and questioned the "governance and dispute-resolution mechanisms".

Instead, Walmart has agreed its own deal to inspect all 279 factories it uses in Bangladesh within six months, and has promised to publish the findings immediately.

Bosses claim this goes beyond the UNI Global Union and IndustriALL deal, pointing out the agreement requires 65% of inspections instead of 100% inspections taking place and argue its own deal means results are published straight away rather than within 45 days.

However, the Walmart deal is not legally binding, does not require the company to offer financial support for fire and safety regulations or blacklist factories unwilling to comply.

The agreement has been criticised by campaigners as a "business as usual" approach, which fails to address the core problems that led to the Rana Plaza factory collapse.

Sam Maher from Labour Behind the Label, said: "Walmart's so-called new programme is simply more of the same ineffective auditing that failed to prevent the Rana Plaza disaster, or the deaths of 112 workers at Tazreen, who were producing Walmart goods.

"The changes demanded by the IndustriALL accord include ensuring that factories are provided with the incentives and investment needed to actually make factories safe and are essential for any real change to occur. What Walmart are demanding is business as usual: a business that has cost lives of over 1,300 workers in the last six months alone."

Walmart has also refused to clarify whether it sourced clothes from the Rana Plaza building, saying only that it had no "authorised" production at the site.

A statement from Walmart said: "The company, like a number of other retailers, is not in a position to sign the IndustriALL accord at this time.

"While we agree with much of the proposal, the IndustriALL plan also introduces requirements, including governance and dispute resolution mechanisms, on supply chain matters that are appropriately left to retailers, suppliers and government, and are unnecessary to achieve fire and safety goals."

Several major UK retailers have declined to sign the agreement, including River Island, Matalan and Peacocks.

However, late on Tuesday night Next, the UK's second biggest clothing retailer, did agree to sign.

On Wednesday afternoon John Lewis and Sir Philip Green's Arcadia group, behind brands including Topshop, Bhs and Dorothy Perkins, also signed the agreement.

Walmart's decision leaves George at Asda, the supermarket's clothing brand, at odds with its position as a founding member of the Ethical Trading Initiative.

The ETI, the UK's biggest alliance of businesses, trade unions and voluntary organisations, has recommended its members sign up to the accord.